The conventional approach in cardiac resynchronization therapy (CRT) involves pacing from an electrode provided close to the right ventricular (RV) apex, an electrode on a transvenous left ventricular (LV) lead, typically in the lateral or postero-lateral vein, and optionally an electrode in the right atrium (RA).
In such a case, the optimal interventricular (VV) delay between RV and LV pacing pulses and the optimal atrioventricular (AV) delay between atrial and ventricular pacing need to be determined. Several prior art solutions to such optimization problems have been suggested. U.S. Pat. No. 5,514,163 optimizes an AV delay based on far field R wave sense (FFRS) duration. U.S. Pat. Nos. 6,751,504; 6,804,555 use the width of the QRS in order to set optimal VV delays. In another document, U.S. Pat. No. 7,848,807, optimal AV and VV delays are determined based on the width of a P wave from a sensed far-field electrocardiogram.
A problem with the prior art CRT is that several heart failure patients do not respond well to the selected biventricular CRT. Thus, there is a need for a CRT that is capable of achieving physiologically suitable heart contraction and thereby lead to improvements also for the non-responding heart failure patient.
U.S. Pat. No. 6,522,923 is directed towards finding optimal AV and VV delays by testing a set of randomly selected AV and VV delays within a defined AV/VV space. The most optimal of the tested AV and VV combinations is found and a new set of randomly selected AV and VV delays are tested within a smaller AV/VV space centered at the most optimal AV/VV-combination. This procedure is repeated multiple times with ever smaller AV/VV spaces until a final optimal combination of AV and VV delays is found.
Zuber et al., Pace 2008, 31: 802-811 discloses a comparison of acoustic cardiography and echocardiography for optimizing pacemaker settings in CRT. It was concluded that for CRT optimization acoustic cardiography provides results similar to echocardiography but with improved reproducibility and ease of use.
Zuber et al., Europace 2008, 10: 367-373 discloses a comparison of different approaches for optimization of AV and VV delay in biventricular pacing. The authors conclude that it is advisable to measure a full grid of AV and VV delays to identify optimal settings rather than optimizing one of the two delays first.
There is, however, still a need for efficient techniques to determine optimal pacing sequence for an implantable medical device having a multipolar cardiac lead.